Liquid pump

ABSTRACT

A piston pump propels liquid through a lumen of a flexible tube segment. The pump includes a first tube clamping member, a first set of tube squeezing members, a second tube clamping member, a second set of tube squeezing members and a synchronizing arrangement for activating the members in a sequential order such that fluid in the tube is displaced in a downstream direction.

BACKGROUND OF THE INVENTION

[0001] This invention relates to pumps and, more specifically, to apiston pump for administering liquids to a patient through a flexibletube.

[0002] Systems for administering liquids to a patient are widely known.However, a variety of different pumps are available for propelling aliquid to a patient, which may differ, among others, in the manner andprinciple in which they operate.

[0003] The present invention is concerned, in preferred embodiments,with two aspects of a system for administering a liquid to a patient. Ina first aspect, the invention provides a pumping mechanism for a pump ofthe aforementioned type. In a second aspect, the invention providescontrol sensors suitable for use with a high-precision, liquidadministering pump.

SUMMARY OF THE INVENTION

[0004] The invention provides, by a first of its aspects, a piston pumpfor propelling liquid through a lumen of a flexible tube segment. Thepump includes a first tube-clamping member, a first set of tubesqueezing members, a second tube clamping member and a second set oftube squeezing members. The members are preferably arranged in adirection from upstream to downstream. Further, the pump includes asynchronizing arrangement for activating the members in a sequentialorder such that fluid in the tube is displaced in a downstreamdirection.

[0005] The sequential activating order of the elements ensurescontinuous and repeatable operation of the pump, and comprises thefollowing steps:

[0006] (a) activating the second tube-clamping member into blocking thetube's lumen and the first tube-clamping member to open the tube'slumen;

[0007] (b) activating the second set of tube squeezing members toconstrict the respective tube portion and the first set of tubesqueezing members to allow expansion of the respective tube portion;

[0008] (c) activating the first tube-clamping member into blocking thetube's lumen;

[0009] (d) activating the second clamping member to open the tube'slumen, and the second set of tube squeezing members to allow expansionof the respective tube portion; and

[0010] (e) activating the first set of tube squeezing members toconstrict the respective tube portion.

[0011] It will be noted, however, that the alphabetic characters used todesignate the steps are provided for convenience only and do not implyany particular order of performing the steps.

[0012] According to one preferred embodiment of the invention, the firstclamping member, the second clamping member and squeezing members of thefirst and second set are axially displaced along an axis normal to alongitudinal axis of the lumen between an open and a blocked position.Optionally, the pressing surface of the squeezing members can be eitherflat or designed shaped for designed squeezing.

[0013] According to still a preferred embodiment, the sectional area ofthe first set of squeezing members is about twice that of the second setof squeezing members.

[0014] By an improved design of the pump, there is further provided acounter member associated with a door of the pump, wherein the first andsecond tube-clamping members clamp the tube against the counter member.Further, the pump includes a flexible cradle associated at least withthe first and second tube-squeezing member. The flexible cradle supportsthe tube at least at the expanded position. At the expanded position ofthe first and second tube squeezing members, the tube is pressed betweenthe cradle and the first and second tube squeezing members so as toassume its shape.

[0015] The synchronizing arrangement preferably comprises a cam andfollower mechanism associated with each of the members, and a revolvingaxle extending parallel to the tube's lumen. According to one possiblearrangement, there are a number of eccentric members mounted on theaxle. The eccentric members are operable to engage the tube clamping andthe tube squeezing members, respectively, for imparting reciprocal axialdisplacement to them in a direction normal to the longitudinal axis.Preferably, the eccentric members are normally biased to engage thetube.

[0016] By another preferred embodiment, the present invention includes adisposal flow set including a drip chamber, an administration tube, avalve and a number of squeezing segments. Each squeezing segmentpreferably includes a stopper in each end. The stoppers are used forlocating the segment in the pumping unit. When a segment loses itsflexibility, another segment can be used.

[0017] By another preferred embodiment, the present invention includes amotor for rotating the axis on which the cams are located.

[0018] According to a second aspect of the present invention, there isprovided a motor and a micro-controller to control motor revolutions inorder to achieve an improved linear delivery of the liquid and toprevent pulsation effects. The micro-controller controls motorrevolutions by using the following algorithm:

[0019] (a) the motor revolution is divided into a number of steps;

[0020] (b) a controller rotates the motor, sequentially from first stepto last step of each revolution, wherein each step or a group of stepshas an individual speed and an individual pause time between steps or agroup of steps;

[0021] (c) the liquid flow, in the output of the pump, in measured ineach step and pause; and

[0022] (d) calculating or changing the speed of each step and durationof each pause, to have the desired flow function.

[0023] The algorithm can be used sequentially during the pump work, orcan be used for calibration to obtain a revolution function—speed andtime for each step and pause—and then use the obtained function torevolve the motor in further work.

[0024] According to another aspect of the present invention, there isprovided a sensor unit for sensing the presence of gas cavities in aliquid flowing through a lumen of a flexible tube segment. The sensorcomprises a transmitter unit having an arced transmitter plate with anapex extending along a line defining a first axis and a receiver unithaving an arced receiver plate with an apex extending along a linedefining a second axis. The two plates are preferably oppositely arcedwith their apexes facing one another defining a sensing space betweenthem, the first and the second axes being essentially perpendicular toone another. Typically and preferably, the sensor is ultrasonic.

[0025] By second preferred embodiment, the tube extends through thesensing space such that each of the arced transmitter plate and thearced receiver plate contacts the tube.

[0026] By another preferred embodiment, the present invention includescommunication capability enabling it to use any communicationinfrastructure to deliver information and receive commands.

[0027] By another aspect, there is provided a dripping sensor forsensing and counting the drips inside the drip chamber.

[0028] By another aspect, there is provided a sensor unit for a pumpadapted for determining the pressure of a liquid flowing within aflexible tube segment. The sensor comprises a tube receiving spaceformed by walls engaging at least a portion of the tube while it isreceived within the space. Preferably, a sensing member projects intothe space for determining deformation-resistance of the tube.

[0029] Preferably, the sensing member comprises a plunger associatedwith a strain gage. The tube receiving space is defined, by a preferredembodiment, between four walls defining a rectangular shape, and theplunger projects through one of the walls. By one specific design, thetube receiving space is defined between two or more arced surfaces.

[0030] Preferably, at a non-pressurized state of the tube, there remainsa known clearance between the walls of the tube receiving space and thetube, whilst the tube is also deformed by the plunger at anon-pressurized state thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to understand the invention and to see how it may becarried out in practice, a preferred embodiment will now be described,by way of non-limiting examples only, with reference to the accompanyingdrawings, in which:

[0032]FIG. 1 is an isometric view of a pump in accordance with thepresent invention comprising a receptacle door being opened prior toengagement with a tube segment;

[0033]FIG. 2 is an illustration of a disposal flow set;

[0034]FIGS. 3a-3 d show, in isolation, the piston mechanism, incontinuous consecutive phases of the pump's operation;

[0035]FIG. 4 is a sectional view of a pressure-sensing unit forincorporation in a pump of the aforementioned type;

[0036]FIG. 5 is a perspective, exploded view of a gas detection sensorfor use in a pump of the aforementioned type; and

[0037]FIGS. 6A and 6B are side views of the device seen in FIG. 4rotated by 90°.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0038] Reference is first made to FIG. 1, in which a piston pump(generally designated 10) is shown, comprising a housing 12, having auser interface unit 14 and a pumping assembly (generally designated 16).Typically, user interface 14 comprises a keypad 18, for input of datasuch as flow rate, flow time, etc., and to initiate or stop the pump,and a display 22.

[0039] The pumping assembly 16 comprises a door 30 pivotally engaged atpivots to a support structure of the pump (not shown). Door 30 comprisesa release lever 35, a biasing spring (not shown) and an engaging hookportion 38 adapted for engagement with a corresponding lateral shoulderof a locking recess formed in the housing 12.

[0040] Door 30 carries also a counter member 15, which in the presentembodiment is spring-biased by means of springs 52. The counter member15 may be a rigid bar covered by a layer of flexible material, or it mayalso be made of a flexible material, e.g. a bar of silicon rubber, etc.The purpose of this counter member 15 will become apparent hereinafter.

[0041] The housing is formed with a receptacle 41 for receiving asegment—between two stoppers 63—of a flexible tube 62 of a flow set 34,such as of a drug administration set, etc. The receptacle 41 extendsacross the housing 12 between openings formed in the sidewalls of thehousing 12. Receptacle 41 is also formed with two-well shaped portionsand a major receptacle portion. It is further noted that the door 30comprises a tube positioning extension 55 for depressing and positioningthe tube 62 within the receptacle 41 at the openings of the housing.Furthermore, the receptacle may be provided with a micro switch (notshown) for generating a signal to the control unit of the pump,indicative of engagement of the pump with a segment of the tube.Suitable sensor means may also be provided to indicate proper closure ofdoor 30. Two openings 37 are formed one in the door 30 and the other inthe housing 12 to locate two parts of an air sensor. A pressure sensor36 is located in the housing 12 between two sides of the tube 62.

[0042]FIG. 2 illustrates a disposal flow set for use with the pump inorder to administer a liquid. The flow set 60 includes an administrationtube 61, which is separated into a number of pumping segments 62 whereineach segment is bordered by two stoppers 63. The stoppers 63 are used tolocate one of the pumping segments in the pump, and when a segment losesits flexibility it can replaced by another segment. The flow set 60includes a dripping chamber 64 that can be used for, inter alia, sensingand counting the drops passing through the chamber using a drip sensor(not shown). The flow set 60 includes a valve 65 and a connector 66 toconnect the set to a patient.

[0043]FIGS. 3a-3 d show, in isolation, the piston mechanism, incontinuous consecutive phases of the pump's operation. The pump includesa first clamping member 71, a first set of squeezing members 76, asecond clamping member 77, a second set of squeezing members 78, and anaxis 74 with a number of eccentric cams 75 installed thereon to elevateand to lower each member according to the pumping sequence in order toclamp and squeeze a tube segment 62 to administer the liquid flow 73from right to left.

[0044] In a first step, (FIG. 3a) the axis 74, with the eccentric cams75, is revolved to a position that elevates the first clamping member 71by an associated cam 75 a, whereby the first clamping member clamps theright end of the tube segment 62. In a further stage of FIG. 3b, theaxis 74 continues its revolution and the first set of squeezing membersare elevated by associated cams 75 b. The squeezing members 76 squeezethe tube segment 62 and force the liquid 73 to move left. In the nextstep (FIG. 3c), by the continuation of the revolution of the axis 74,the second clamping member 77 is elevated by an associated cam 75 c andclamps the tube segment 62 in the left end of the squeezed area.Meanwhile, the second squeezing set 78 is still elevated from theprevious sequence, by the associated cams 75 d, and starts to move downto ensure the continued flow of the liquid 73.

[0045] In the last sequential step (FIG. 3d), by the continuation of theaxis 74 to revolve, the second set of squeezing members 78 are finishedelevating and, in the meantime, the first set of squeezing members 76and the first clamping member 71 are lowered by the associated cams 75 aand 75 b. While the remaining liquid 73 is pushed to the left, a newliquid 79 from a container (not shown) fills the right released part ofthe tube segment 62, ready for the next sequence of the pump when thesecond set of squeezing members 78 and the second clamping member 77 arelowered and the first clamping member 71 is elevated.

[0046] For best performance, preferably the squeezing size area of thefirst set of squeezing members 76 is about double the size of thesqueezing size area of the second set of squeezing members 78, so as toensure continuous propagation of liquid in a downward direction, wherethe volume of liquid received within the tube segment corresponding withthe area of tube squeezing members 76 serves as a reservoir of liquid.

[0047] The cams are angularly diverted such that at least one or more ofthe cam followers constitute the first tube clamping member, one or moreother cam followers constitute the second tube clamping member, severalother cam followers arranged in the same orientation constitute thefirst set of tube squeezing members, and several other cam followersarranged in the same orientation constitute the second set of tubesqueezing members.

[0048] Different parameters are maintained similar to the previousembodiment, e.g., the tube blocking cam followers engage the respectivetube segment so as to essentially block the tube's lumen, whilst thetube squeezing cam followers engage the respective tube segment to onlypartially squeeze the tube's lumen. This may be achieved by differentlyforming the tube-engaging surface of the cam followers, or by shorteningtheir lengths or by different forms of the cams.

[0049] In FIG. 4 of the drawings, there is illustrated a pressuresensing device 170 incorporated into the pump in accordance with thepresent invention, or other liquid administrating pumps, and is suitablefor placing within one of the cavities 46 or 48 formed in the housing12. The sensor unit 170 comprises a U-like receptacle 172 dimensioned soas to comfortably accommodate tube 62, with a suitable counter member 50closing the structure from above. A plunger 174 projects into the space176 confined within the U-like receptacle 172 through a suitable openingat a bottom wall thereof 178 and is associated with a pressure sensinggauge 180, e.g. a piezo-electric gauge, string gauge, etc., fordetecting pressure applied thereto by the tube 62, depending on itsinternal pressure applied by the liquid flowing through its lumen.

[0050] The arrangement of the sensor 170 ensures that local deformationof the tube is converted into terms of pressure without influence ofoverall deformation of the tube caused by the internal pressure of theliquid, this owing to the support walls of structure 172 preventingundesired deformation of the tube.

[0051]FIGS. 5 and 6 illustrate a sensor for detecting the presence ofgas, typically air, flowing within the liquid carrying tube. The device(generally designated 190) is suitable for insertion within one of thecavities 46 or 48 of housing 12 and comprises a transmitter unit 192having an arced transmitter plate 196 and a receiver unit 194 having anarced receiver plate 198, with the two plates 196 and 198 beingoppositely arced with their apexes facing one another defining betweenthem a sensing space 200 (FIGS. 6A and 6B). In order to achieve sensingfocus, the two plates 196 and 198 are preferably perpendicular to eachother. Typically, the sensor is ultrasonic.

[0052] The arrangement is such that the entire cross-section of the tubeis covered by the ultrasonic waves, thereby any air cavities, even ifsignificantly small with respect to the cross-section of the tube, andeven if not flowing axially centered within the tube, are detected.

[0053] Whilst preferred embodiments have been shown and described, it isto be understood that it is not intended thereby to limit the disclosureof the invention, but rather it is intended to cover all modificationsand arrangements falling within the spirit and the scope of theinvention, mutatis mutandis.

What is claimed is:
 1. A piston pump for propelling liquid through alumen of a flexible tube segment, the pump comprising: a firsttube-clamping member; a first set of tube squeezing members; a secondtube-clamping member; a second set of tube squeezing members, saidmembers arranged in a direction from upstream to downstream; a motor;and a synchronizing device operably associated with the motor and saidmembers, the synchronizing device operable to activate said members in asequential order such that fluid in the tube is displaced in adownstream direction.
 2. The piston pump of claim 1, further comprisinga disposal flow set comprising a drip chamber, a valve, and a flexibletube including at least one squeezing segment defining two ends, whereineach end of the at least one squeezing segment is associated with astopper.
 3. A piston pump of claim 2 wherein the sequential activatingorder comprises: activating said second tube clamping member intoblocking the lumen of a tube of said flow set tube and said first tubeclamping member to open the lumen of said tube of said flow set tube;activating said second set of tube squeezing members to constrict arespective tube portion and said first set of tube squeezing members toallow expansion of said respective tube portion; activating said firsttube clamping member into blocking said tube's lumen; activating saidsecond clamping member to open said tube's lumen, and said second set oftube squeezing members to allow expansion of said respective tubeportion; and activating said first set of tube squeezing members toconstrict said respective tube portion.
 4. The piston pump of claim 3wherein the pressing surface of said squeezing members is designed fordesigned squeezing.
 5. The piston pump of claim 3 wherein the squeezingarea of said first set of squeezing members is about twice of the areaof said second set of squeezing members.
 6. The piston pump of claim 3wherein the synchronizing device comprises an axis and a number ofeccentric cams operably associated with the axis, a cam for each saidclamping or squeezing member, for moving said members up and down. 7.The piston pump of claim 6 wherein the motor is operable to revolve saidsynchronizing device.
 8. The piston pump of claim 1, further comprisingan ultrasonic sensor operably associated with the flexible tube segmentfor detecting air in the liquid.
 9. The piston pump of claim 1, furthercomprising a communication device operable to use any communicationinfrastructure for delivering information and receiving commands. 10.The piston pump of claim 2, further comprising a dripping sensor forsensing and counting the drips passing through said dripping chamber.11. The piston pump of claim 2, further comprising a sensor unit adaptedfor determining the pressure of a liquid flowing within said flexibletube.
 12. The piston pump of claim 11 wherein the sensor unit defines atube receiving space formed by walls engaging at least a portion of saidtube and comprises a sensing member projecting into the space fordetermining deformation-resistance of said tube.
 13. The piston pump ofclaim 12 wherein said sensing member comprises a plunger associated witha strain gage and said receiving space is defined by a rectangular shapeand said plunger projects through one of the walls of said tube.
 14. Thepiston pump of claim 7 wherein said motor is revolved by a controllerinto a nonlinear revolution to achieve linear flow of liquid, by usingan algorithm for revolving a motor in a specific nonlinear revolution,comprising: the motor revolution is divided into a number of steps; acontroller rotates said motor, sequentially from first step to the laststep of each revolution, wherein each step or a group of steps has anindividual speed and an individual pause time between steps or a groupof steps; the liquid flow, in the output of the pump, is measured ineach said step and in each said pause; calculating or changing the speedof each said step and duration of each said pause, to have the desiredflow function; and storing the function of the nonlinear revolution ofsaid motor, in a memory.
 15. The piston pump of claim 13, wherein saidalgorithm is used sequentially during said pump work.
 16. The pistonpump of claim 15 wherein said algorithm is used for calibration toobtain said function of nonlinear revolution and said controller usesthe obtained function to revolve said motor in further work.
 17. Amethod for controlling a pump in which a flexible tube is disposed fordelivery of a liquid, comprising: activating a second tube-clampingmember into blocking a lumen of the tube and a first tube-clampingmember to open the lumen of the tube; activating a second set of tubesqueezing members to constrict a second portion of the tube and a firstset of tube squeezing members to allow expansion of a first portion ofthe tube; activating the first tube-clamping member into blocking thelumen of the tube; activating the second clamping member to open thelumen of the tube, and the second set of tube squeezing members to allowexpansion of the second portion of the tube; and activating the firstset of tube squeezing members to constrict the first portion of thetube.
 18. An injection apparatus comprising, in combination, a pump forpumping liquid through a lumen of a flexible tube; wherein the pumpcomprises: a motor; a first tube-clamping member; a first set of tubesqueezing members; a second tube-clamping member; a second set of tubesqueezing members, said members arranged in a direction from upstream todownstream; and a synchronizing device operably associated with themotor and said members, the synchronizing device operable to activatesaid members in a sequential order such that fluid in the tube isdisplaced in a downstream direction; and wherein the flexible tubecomprises: a drip chamber; a valve; and at least one squeezing segmentdefining two ends, wherein each end of the at least one squeezingsegment is associated with a stopper.